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  • newby needs advice

    Dad and I built these cabinets 30 years ago when I went off to college. They have some wear, but work well for me.

    I have replaced the drivers with GRS BT2-8 3-3/8" Horn Loaded Bullet Tweeter (80W) and Goldwood GW-206/8 6-1/2" OEM Woofer 8 Ohm (90W) with a no name crossover at 3,500 Hz(100W). The sub is just a Goldwood PAC8 8" in a sealed box with pillow stuffing. I have Fosi Audio B30C amplifer (50Wx50Wx100W) that I source from a laptop over bluetooth. I bought these parts so that I wouldn't overdrive anything ever. I like to "turn it up to 11" and not release the magic smoke.

    (Yes, if you haven't notice, my theme is "cheap". I don't mind spending money, but I loath wasting money.)

    I'm not an audiophile. I don't have the ears to notice the impact of bluetooth. I've also done testing with analog cables and noticed no difference.

    I really like this setup at medium volumes (100% on the amp and 50% on the bluetooth stream). I like how crisp these horn tweeters are. I really like the sound of acoustic folk (Mandolin Orange); I can feel the guitar. The bass is punchy and the highs (like finger rub on the strings) is right there.

    Now the problem: At high volumes the tweeter hurts. It sounds like maybe digital issues, but happens even when I test with an analog source. I think it's just a cheap tweeter distorting way below it's rating. I want something that sounds better at higher volumes. I have tried a MK422 in place of this entire speaker and it isn't loud enough, and the highs are not bright enough for me. (I may be misusing those terms).

    Can anyone recommend what I may have done wrong or a different tweeter that is as bright, but more mellow when I crank it up? I bought an L-pad thinking that the tweeter was just too loud, but I haven't installed it yet, because the more I listen, the more I think it is distortion, not just volume.

    I'm considering "Peerless by Tymphany D19TD-05 3/4" Poly Dome Tweeter" because it has lots of positive reviews.


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  • #2
    I'll hazard a guess. Cheap horns often have a ragged frequency response. Probably there are peaks that are hurting your ears. If so, you need to measure and use notch networks to flatten them.
    Francis

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    • #3
      "These cabinets"? Where? How about a picture?

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      • #4
        No idea why the picture didn't show for other people. I pasted it in, then could see it. Checking it with privacy mode it was missing. I uploaded it and now it seems to work.

        Comment


        • djg
          djg commented
          Editing a comment
          Thank you. See them now.

      • #5
        I think you need to back up a moment and think what you are trying to achieve. What have you read about the speaker design process? Do you understand why a $3 piezo horn sounds like it does, why 3500 is a terrible choice for that woofer, why the raised edge is a bad idea etc.? We all built speakers much like yours for our first project, so I am not trying to be gruff. That experience, and what you are hearing now, is what got us to back up and learn about the science involved. Our next pair was better. You are thinking correctly to attack the tweeter, but it needs to include the crossover.

        Yes, the Peerless is a vastly better tweeter. With a proper crossover might make a nice little system using your woofer. So might some of the Dayton tweeters on the budget end. Key :proper crossover Picking the drivers is maybe 5% of designing a speaker. I would not know without doing several hours of design and modeling work. Heck the $3 T-24 paper cone tweeter was used in $1000 speakers back in the day. The original Peerless version is still working happily in my Tanburgs.

        What is it you are really asking? If you can just drop in another miss-matched tweeter? You can. It may be better. ( about any will be). Are you interested in learning how we design speakers, willing to spend weeks reading, testing, building, buying test equipment?

        The comment "you need to measure" Truth yes, but that assumes you have the equipment. Filter the horn.? Well, you may be able to make a $3 horn sound like a $5 horn by putting in $20 worth of filters after spending $300 on test equipment.


        If you just want a better set of speakers really cheap, I suggest e-bay. I have seen some fantastic pairs go for almost nothing.

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        • #6
          Maybe something like these: https://midwestaudio.club/spotlight/.../cabriniredux/

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          • #7
            Looks like a good beginner project. If you follow along with design, you can really make a jump on understanding. Reproduce what they did, but knowing the outcome.

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            • #8
              I would try adding a notch at 4k on the woofer before changing much else. There's a couple ways to do it, and it's easy. What I'm saying is that the woofer peak at 4k might very well be what you are hearing. It needs to be notched, even if the tweeter is not great. Should take about $10 worth of parts. Maybe less.

              https://www.parts-express.com/pedocs...-info-3665.pdf

              Another thing that should help is adding some better damping material to the box. I like dense fiberglass like the stuff used in ceiling tiles. Other stuff will work too. Try stuffing it with an old T-shirt, socks, etc.
              Last edited by rpb; 08-21-2020, 09:15 PM.

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              • Joe Batt
                Joe Batt commented
                Editing a comment
                I'll experiment. First with no tweeter, then with stuffing. That would demonstrate what you (and others) are suggesting. I didn't think about the woofer making this noise. I couldn't even put my finger on the frequency or noise, just that it makes me wince.

            • #9
              The BT2 is not a Piezo it's a mylar dome CD, but like most piezos it is a super tweeter which means it should NEVER see anything below 5khz minimum, and ideally something a bit higher than that.
              That means the tweeter isn't being used properly, the crossover is wrong for the application, the enclosure is less than ideal, and who knows if the mid is capable of crossing higher or would work well with a totally different tweeter like a soft dome.
              So maybe better to start over with a different design maybe a kit, and if the OP likes more efficient designs then maybe something from the DIYsoundgroup would be suitable
              Paul O

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              • #10
                (EDIT: Oops is right !)
                (I had the 6" & 8" GW drivers flopped in my sim, sorry. Asterisks show OLD info - look for "NEW" info.)

                A few observations:
                Your most MAJOR problem would be the bullet (@ 100dB !) is runnin' at least +12dB louder than your 6". (With every 3dB being a doubling of power, that means that your highs (above 3kHz) should be SCREAMing - 16 times louder than your bass and mids.) Even if the tweeter was clean, that would sound like distortion to ME.
                I'd wire that L-pad in there.

                *Once you get the tweeter dialed down -16 to -18dB or so, your next issue is that your (3.5k) XO is (probably) actually boosting your woofer's 3k cone breakup. Adding a Zobel across the woofer (in parallel w/its terminals) should help w/that. I'd use an 8ohm resistor (10w, not 1w) and an 8uF cap (a cheap "npe" is fine).
                NEW - With the tweeter down -12 to -14dB, the FOUR kHz breakup is a big problem. A Zobel can't really fix it (like it could on the 8").
                NEW - The coil should probably triple in size, to 2.0mH (low DCR (cored) would be better).
                NEW - Also the cap (on the LP) should be doubled to 6uF. This doesn't really give you a "good" freq. resp., just one that's better than what you've been listening to. (Sorry for flopping the drivers. Again, sorry.)

                Box modeling shows your 6" can likely reach down to 70Hz, whereas your "sub" poops out @ 80Hz. "Room-gain" (esp. w/your corner placement) helps that, but that can't "create" your missing bottom octave for you.

                You can certainly buy a better tweeter, "mid", and "sub" for the $12?, $18?, and $40? you spent on your driver choices.
                A 3/4" tweeter is not indicated in your situation. You want a 1" (or 1-1/8") dome, that can cross down at 2k (even like Dayton's 275-070 "Silkie").
                Your sub is fairly ineffectual.
                Last edited by Chris Roemer; 08-22-2020, 12:38 PM.

                Comment


                • rpb
                  rpb commented
                  Editing a comment
                  Try adding an EQ notch centered on 4k. That will notch both the woofer and the tweeter.

                • rpb
                  rpb commented
                  Editing a comment
                  Due to the non flat impedance, the x-overs don't follow textbook curves. If your computer has Excel, you can download PCD to simulate x-overs. It's free.

                • Joe Batt
                  Joe Batt commented
                  Editing a comment
                  I was unable to find any sort of response chart for the sub. Why do you think that it poops out at 80Hz?

              • #11
                After listening to that setup for however long you've had it, a more accurate speaker may come across to you as dull and lifeless. Listen to it for a while before judging it, you will adapt and begin to appreciate a better sound.

                Comment


                • Joe Batt
                  Joe Batt commented
                  Editing a comment
                  At normal listening levels, I completely agree. I'm a programmer and the music is playing not too loudly in the background all day long. I want to hear and feel the instruments, and not the words. The vocals are distracting. So during the day, my speakers are great, then at the end of the day I crank them up to relax and they sound like crap.

                  Yesterday I did a listening session with a Klipsch RS-3s system. I could hear what I'm missing in the vocal range.

                  I've got these MK442's that I'll use for a few weeks to decide if I should build or buy. (today my guess is that the 30 year old speakers will move to the shop. I'll staple some screen over the fronts to keep the mice out. They have long outlived their college dorm expectations.)

              • #12
                The sound inside the box is very loud, and bounces around inside if there's nothing to absorb it. Some makes it out through the wood. Some will strike the back of the cone and be combined with the new sound. I absorb as much as possible.

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                • #13
                  Also, if you ran a 3"id x 8" long port tube out the back of the sub box, you'd extend its bottom-end reach from 80Hz down to 30Hz. That's almost an octave and a half (or about 18 keys on a piano).

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                  • #14
                    I'm guessin' that your "Goldwood PAC8" is, in fact, Goldwood's "GW-8PC-8" (#290-356).

                    Using the FREE "WinISD" ( from linearteam.org - sc ) I ran a box sim w/THAT 8" in a closed box of about 1.6cf (simmed as 1.9cf - stuffed).
                    It does beat 80Hz, but not 70.

                    If you add a port though (tuning the box to the mid 30s), then its F3 is in the low 30s.

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                    • Joe Batt
                      Joe Batt commented
                      Editing a comment
                      Actually it's this $9 sub in a cabinet made of scrap, so we aren't complaining at all: https://www.parts-express.com/goldwo...-coil--299-524

                      We did some frequency sweeps and there was a bad resonance at 85ish Hz (and 170 and 340...), but we don't know (or care much) if it's this room, the cabinet or the driver. I keep the crossover to the sub at the lowest (80hz I think).

                  • #15
                    Was the x-over replaced, or is it from 30 years ago? Caps go bad in that length of time.

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